DETERMINATION OF ANOMALOUS ELASTIC-SCATTERING OF GAMMA-RAYS OF ENERGIES CLOSE TO K-SHELL BINDING THRESHOLDS

''Anomalous'' scattering corrections to Rayleigh scattering amplitudes calculated in the form factor approximation are of considerable interest in the study of elastic-scattering of gamma-rays and X-rays. When photon energies are close to binding energies of atomic inner shell electrons, the corrections have relatively large magnitudes. But under such conditions, the comparatively weak elastic-scattering contribution cannot be resolved even with semiconductor detectors from most of the components of target K beta(2)' X-rays. It is shown that elastic-scattering in such an interesting energy regime can be determined with the help of a least-squares-fitting procedure for the composite spectrum. The procedure is illustrated with a detailed study of 81.0 keV gamma-ray scattering from gold having a K shell binding energy of 80.723 keV. Data were obtained at several angles with gold and other targets of different atomic number Z.